Dipolar Glass State inK1−xNaxTaO3

The static dielectric susceptibility of ${\mathrm{K}}_{1-x}{\mathrm{Na}}_x\mathrm{Ta}{\mathrm{O}}_3$ and its field derivatives depend critically on temperature above the transition temperature $T_g$. Below $T_g$, the susceptibility is dispersive and reveals relaxation between marginally stable states. The transition from the paraelectric to the disordered polar phase thus has dual aspects, criticality and metastability, just the same as spin systems with infinite-range interactions.